Internal combustion engines, particularly diesel engines, are plagued by cold starting problems. One effective method of improving cold starting is to inject a starting fluid such as an ether based fuel into the engine during cranking. The present invention is directed to an improved dispenser for automatically injecting starting fluid during engine startup without operator intervention.
In the past, several types of starting fluid dispensers have been used in connection with starting fluid injection. Originally, dispensers were manually controlled by the operator. Such dispensers have several disadvantages. Since they rely on operator activation, these dispensers inject a highly variable amount of starting fluid into the engine. For example, the operator can fail to operate the dispenser or can operate it improperly, thereby injecting inadequate starting fluid for prompt starting. Furthermore, the timing of the injection of starting fluid into the engine can be important, and the timing of a manually operated dispenser is no more consistent than the operator. Moreover, such dispensers can be abused by the operator to inject starting fluid into the engine when running for a momentary increase in power. This practice, known as "ether jockeying" can result in engine damage.
In response to these disadvantages of manually operated dispensers, Davis in U.S. Pat. No. 3,960,131, disclosed an automatic engine starting system which automatically dispenses starting fluid in a series of pulses during engine cranking. The Davis system employs a measured shot valve which dispenses a measured volume of fluid with each cycle. The valve is automatically driven to repeatedly dispense measured volumes of starting fluid during engine cranking.
The Davis device suffers from the important disadvantages that it is a pulsed flow system. It has been discovered that the pulsed flow produced by the measured shot valve results in a wide range of fluid pressure at the point of injection into the engine. This variation in pressure results in a varying injection rate and efficiency of atomization; both of which are thought to adversely effect the uniformity of delivery of starting fluid to the engine.
Furthermore, the measured shot approach of Davis results in erratic delivery of starting fluid to the engine following termination of cranking. After cranking stops, the volume of fluid remaining in the valve is dispensed to the engine. However, this volume can vary widely, depending on the point in the valve cycle at which cranking stops. For example, if cranking stops near the end of the filling of the measured volume, then almost an entire measured shot of fluid will be dispensed following cranking. On the other hand, if cranking stops near the beginning of the filling of the measured volume, a much smaller amount of fluid will be dispensed.
Moreover, a measured shot valve such as used by Davis is relatively complex. The valve itself is often more expensive to produce than continuous flow valves, and the valve control mechanism must include means for cycling the valve. Thus, the Davis approach is relatively expensive to produce as well as erratic in operation.